Design and analysis on SMT QFN silicone keypads

Conductive silicone keypads are widely applied in many electrical products. However, they are still followed the plug-in mounting design up to now. In this study, in accordance with the development direction of Surface Mounted Technology (SMT) microelectronics packaging components, a SMT silicone keypad in quad flat no lead (QFN) form is proposed. First, the SMT silicone keypad is modeled by using the finite element analysis software, and then the relationship between the pressing force and the key displacement is discussed. Second, the mechanical stress distribution of the SMT QFN silicone keypad is simulated and analyzed, and further the structure failure possibility is discussed. The results show that the fatigue life of components is mainly affected by the fatigue weak link, and the stress concentration area of the fatigue life is the lowest. According to the simulation and analysis, the structure of the proposed SMT silicone keypad should be further optimized to minimize the structure stress concentration.